1. Field of the Invention
The present invention relates to an in-cylinder direct-injection spark-ignition engine with an electronic concentrated engine control system, employing a variable swirl-and-tumble control mechanism and an electronically-controlled fuel-injection system used to switch between a homogeneous combustion mode using tumble airflow and a stratified combustion mode using swirl airflow.
2. Description of the Prior Art
In recent years, there have been proposed and developed various in-cylinder direct-injection spark-ignition engines in which fuel is injected directly into the engine cylinder. The direct-injection spark-ignition engine uses at least two combustion modes, namely an early injection combustion mode or a homogeneous combustion mode where fuel-injection early in the intake stroke produces a homogeneous air-fuel mixture, and a late injection combustion mode or a stratified combustion mode where late fuel-injection delays the event until the end of the compression stroke to produce a stratified air-fuel mixture. One such cylinder direct-injection spark-ignition engine has been disclosed in Japanese Patent Provisional Publication No. 8-35429. This patent provisional publication teaches the provision of a non-circular piston bowl having a reentrant portion and a pair of intake ports, namely, a straight intake port with a so-called swirl control valve and a helical intake port.